The blind rivet of the instant invention is an improvement on the composite rivet disclosed in U.S. patent application Ser. No. 384,873, filed June 4, 1982, now U.S. Pat. No. 4,478,544 for Composite Rivet, and assigned to the assignee hereof.
Carbon fibre reinforced materials are now widely used in the aircraft industry for both control surfaces and airframe structural components. However, the use of such carbon fibre reinforced resins in blind rivets has been limited by the difficulty of properly forming the blind head. One characteristic of composite materials utilizing carbon fibres is that the material often exhibits a rough finish after reforming due to protrusion or breakage of the carbon fibres. While structural integrity of the material may not be compromised, the end product is abrasive and aesthetically unsatisfactory. When such material is employed in the reformable head of a blind rivet, the problem becomes acute since the blind head extends above the surface of the workpiece.
Another problem that must be addressed is that plastic cold flow of the rivet components tends to reduce clamp-up forces on a workpiece. Thus, pretension of the rivet is highly desirable to offset ultimate relaxation of the tensile forces.